Paper industry

Repro paper.

Also called offset or printing paper. It is one of the most common papers on the market and is manufactured in large quantities. These sheets are made with a small amount of cellulose and a great deal of filler, which facilitates printing, their main application. The most common grammages range from 70 to 90, although they can be as high as 100 grams. Manufacturers seek the greatest possible degree of whiteness for this material, largely obtained with the help of fillers. On the other hand, since it is used for applications that do not require a great deal of handling it is only strong enough to go through the printer or to be folded.

The evolution in the manufacture of this material has led pulp factories to be integrated into paper factories to reduce costs, with the entire process being conducted in the same facility. The paper is normally produced in 9 to 10-meter-wide runs at a speed of 2000 meters per minute.

Couche or coated paper.

Coated paper is manufactured with more short than long fiber, and the filler is joined to the fiber using a binding agent, which may be synthetic or natural (normally calcium carbonate). A coated layer is applied to the cellulose, yielding better printing and resolution results (on account of the higher screens). This is because the ink remains on the surface, and consequently, the post-printing result is shinier and more colorful.

The most common option is white-coated paper because if the coating cracks, the background color is not apparent (although the color difference will be noticeable in color coatings). There is the matte or semi-matte finish, which involves solving the application of surface ink, although in this case, the ink is less shiny.

In terms of strength, the high amount of fiber and short fiber makes it quite low, as opposed to the high printing quality. Production runs are normally between 7 and 8 meters wide in the machine, with speeds of up to 1000 meters a minute.

Tissue paper.

This material is highly absorbent and soft. Its water resistance will depend on the sub type in question: paper used to manufacture handkerchiefs or napkins must withstand liquids to prevent them from falling apart when used, whereas paper used for napkins must dissolve easily. To achieve this, different treatments are applied during the manufacturing process and they are normally produced with virgin fiber.

Colored tissue paper is made with a mass-dyed process. Prints and reliefs are applied offline once the paper has left the machine. This paper is normally made in rolls with a width of 4 meters that is subsequently cut to order at a maximum speed of 2000 meters a minute.

Newsprint.

Newsprint paper, as its name implies, is used to print newspapers. Its life cycle is short, normally one day, for obvious reasons. For this reason, material quality does not need to be high and the paper is manufactured with the mechanical pulp containing residue, as the paper does not need to be white. It is rarely colored, although if it is the color is applied using mass-dying.

On account of this low quality, ink finishes are precarious (this is noticeable, for example, in the printing of low-resolution photographs or in the ink, which has a dull finish). The paper’s mechanical properties are also virtually non-existent, having the basic strength needed for the reader to turn the pages of the newspaper without tearing them.

Cardboard.

Cardboard is a product made with paper, although this is not always evident on account of its thickness. It is made with raw, unbleached wood pulp, leading it to maintain its original brown color. As appearance is not a concern, it is normally made with recycled material. Cardboard is comprised of three layers of paper, two smooth outer layers, and a corrugated inner layer, the latter providing it with its characteristic strength. In terms of mechanical properties, the corrugated layer makes the material strong, although, on the other hand, it is not suitable for printing, since it may get crushed depending on the pressure applied to it.

One subgroup inside the cardboard is Kraft paper, made of a single layer of paper. It is used for thinner packing since it is easy to handle and also to adapt to the specific product to be wrapped.

Paperboard.

This material is used to make most food containers, such as cereal or biscuit packaging. Paperboard are made of very short fibers which are not usually virgin since the inner layer does not need to be white. As a rule, it has a coated layer that serves as a printable surface and also guarantees the appearance of the external and visible side to make the product attractive to consumers. Grammage will vary depending on the target industry or the specific application or product. In terms of mechanical characteristics, it must be strong enough to withstand the product being opened and closed until it is no longer used.

Fine art paper.

Fine arts paper must have different technical and functional characteristics depending on the artistic technique. This material was devised as a more economical option for canvases: in fact, some of these papers featured excellent characteristics and can withstand almost a Century without turning yellow.